Stabilization of vinyl acetate



I Patented Dcc.-5, '1939 UNITED STATE-S;

(PATENT OFFICE 2.152.528 STABILIZATION OF VINYL ACETATE Gelu S. Stamatofi, Arlington, N. J., assignor to E. L du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing.

Application July 29, 1938,

Serial No. 222,068

3 Claims.

i provide a polymerization inhibitor directly soluble in vinyl acetate without the assistance of a third substance as an intermediary. A stilliurther object is to provide such a polymerization'inhibitor which is not volatile at the temperature of distillation of the vinyl acetate and, hence,- is

readily separated completely from the vinyl acetate. Other objects of the invention'will be apparent from the description given hereinafter.

The above objects are accomplished according to the present invention by adding to monomeric vinyl acetate to be stabilized a substan i:e .from the group consisting of rosin and the copper, zinc, magnesium, aluminum, and cobalt resinates. It is preferred to employ copper resinate as the inhibitor.

Those skilled in the art will appreciate that rosin of ordinary commercial grades, although a mixture of somewhat indefinite composition, is compwed chiefly of abietic acid, approximately 80-90%, and the metal resinates of commerce are essentially abietates containing various impurities in varying but relatively small proportions. Since rosin-and metal resinates of commercial grades are entirely satisfactory for the purposes of the present invention and considerably more economical than pure abietic acid or metal abietates, it is preferred to use them as a matter of economy and convenience.

The effectiveness of the herein considered sub- 4 stances as inhibitors or preventives of polymerization of vinyl acetate is demonstrated by the following test:

Monomeric vinyl acetate containing the inhibitor is placed in a flask fitted with a ground- 45 joint glass condenser and boiled under reflux for 24 hours. The flask is them emptied into water which is boiled to expel unpolymerized monomer. The residuecontaining the inhibitor and any polymer formed is dried and weighed. By de- 50 ducting the weight -of the inhibitor from the weight of the residue, the weight of the polymer formed during the 24 hours heating is thus established.

Results with various inhibitors of the present 55 invention in varying proportionsare given the t ive inhibitors whenpresent in only very small table below, proportions being given by weight:

Inhibitor added to monomer Percentage polymer grilled 6 0111'80 Substance Percentage naming I Copper resinate--. 0. 1 0.002 Do"--- 0.05 0.070 8'8? 3-923 I 01005 2125 m 0.2 0.5 0.1 0.762 0.2 1.14 0.2 0.89 Rosin 0.2 0. 35 Control batch No inhibitor 37.5 m

It will be understood that the above proportions of inhibitor are merely illustrative and that the proportion of 'theinhibitor used in any particular instance will depend upon the conditions 20 to which the monomeris to be exposed and upon the thoroughness 50f the inhibitory action required, During .'c;listillation-,' the percentage of inhibitor builds up as the volume of monomer in the flask or pot decreases.

Copper resinate is the preferred inhibitor and 25 the amount or this substance required to prevent polymerization of vinyl acetate monomer during prolonged storage at temperatures up to 40 C. is of the order of 0.01% by weight of the vinyl acetate. The amount of copper resin'aterequired to prevent appreciable polymerizationduring distillation at atmospheric pressure is of the order or 0.1%. With monomer containing unusually large amounts of aldehydes these proportions should be increased somewhat. The other substances will be used in greater proportions to obtain the same effectas can be deduced from a consideration of the table given above. a

An advantage of the present invention is that the inhibitors are inexpensive and readily soluble in monomeric vinyl acetate in efiective proportions, requiringno third substance to promote solution. Further, they are not volatilized with the vinyl acetate during distillation of the latter v and are thus readily removed therefrom prior to any process of polymerizing the vinyl acetate. In addition, these substances are extremely efiecamounts.

As many apparently widely different embodiments of this invention may be made without departing from tile spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodimentsfthereol except as 2. Method of inhibiting poiymerimtion oi defined in the appended claims. monomeric vinyl acetate which comprises adding I claim: thereto, in inhibitor amounts copper resinate. 1. Method of inhibiting polymerization of j-- 3. Method of inhibiting polymerization of 5 monomeric vinyl acetate which comprises adding monomeric vinyl acetate which comprises adding 5 thereto, in inhibitor amounts, a substance selected thereto 0.01% to 0.1% of copper resinate by from the group consisting of rosinand the copper, weight of the vinyl acetate. zinc, magnesium, aluminum, and cobalt resinates. I Y GELU 8. STAMA'IOH'". 

